Code Simplicity Open Source Design

8/12/2019 Code Simplicity Open Source Design

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Code Simplicity:Software Design In Open Source

Projects

Max Kanat-lexandermax!codesimplicity"com


2/27

#efore $%e S%ow

I tal& 'uic&ly

Stop me if you don(t understand

lso stop me if you need examples

)uestions or disagreements at end

Points will *e fast+ *ut still important

More detail on e,eryt%ing at my *log:

%ttp:www"codesimplicity"com Some of t%ese t%ings you may already &now+w%at matters is pointing t%em out as important"
http://www.codesimplicity.com/http://www.codesimplicity.com/


3/27

.%o am I/

ssistant Project 0ead for #ug1illa

.riter of Code Simplicity 0ong-time programmer and system administrator

Data comes from:

2xperience programming and designing #ug1illa 3experiment4

Inter,iewing many programmers

5eading extensi,ely wit% analysis

Data collection is difficult *ecause of t%e timeframe ofsoftware projects"

I spea& ,ery definitely+ *ut please ma&e up your

own mind a*out t%e t%ings I am saying"


4/27

.%at Is Software Design/

dministrati,e Decisions

.%at programmer to put w%ere

De,elopment timeframes

etc"

Coding

Technical Decisions

.%at language to use

.%at tec%nologies to c%oose

etc"


5/27

$%ere Is 6o Science of SoftwareDesign

Science re'uires:

0aws

Proof

5esults

Many met%odologies+ no science:

3.aterfall4

3gile4

etc"


6/27

6ot going to pro,e anyt%ing today+ just s%ow

Can pro,e+ t%oug%+ in ,arious ways $%ere are similar ideas out t%ere+ *ut t%ey are

not t%e same as w%at I am going to tal& a*out

0argely t%ey are not low-le,el enoug% Se,en Principles:

%ttp:c7"comcgiwi&i/Se,enPrinciplesOfSoftwareDe,elopment

$%ey tell you whatto do+ I only %elp you ma&edecisions for yourself and try to tell you why"

I did not deri,e from any of t%ese met%odologies+*ut t%e *its of t%em t%at wor& could *e deri,ed fromw%at I am going to tell you"
http://c2.com/cgi/wiki?SevenPrinciplesOfSoftwareDevelopmenthttp://c2.com/cgi/wiki?SevenPrinciplesOfSoftwareDevelopment


7/27

.%y 8a,e a Science of SoftwareDesign/

8elp Ma&e $ec%nical Decisions

Whydo some t%ings 3wor&4 and ot%ers don(t/


8/27

5esults

#ug1illa

Impro,ed My Own Programming

5esol,ed e,ery 'uestion

#roug%t no,ices to understand why

2xplained difficulties and 3war stories4 ofexperienced programmers


9/27

6ot #rainwas%ing or Mar&eting

6ot going to tell you w%at decisions to ma&e+just going to gi,e you information t%at will %elpyou ma&e t%em

$%is differs from met%odologies #u11word-free


10/27

9OSS ,s" Proprietary

$%e *asics are t%e same+ *ut application can *edifferent"


11/27

Purpose Of Software

To help people 6e,er 3to %elp t%e computer4

Specific software is 3$o %elp people *la%;4

Stated purpose s%ould *e:

S%ort

Simple

Specific

6eeded

9ollowed 2xactly


12/27


13/27

Primary 0aw: 9uture

$%ere is more future t%an present

9uture is composed of infinite series of presents

$%e future is more important t%an t%e present

2ffort spent on design s%ould *e proportional to%ow muc% future time t%ere is in w%ic% youexpect t%e software to exist

Planning to re-write is unnecessary


14/27

9uture: Known ,s" =n&nown

Known =n&nown

6ear9uture

9ar 9uture

9uture5e'uirements

Conse'uences

Software %as long time lines


15/27

0aw Of C%ange

$%e longer your software exists+ t%e morepro*a*le it is t%at any piece of it will %a,e toc%ange

Means t%at as time goes on+ everypiece is li&ely toc%ange


16/27

0aw of Defect Pro*a*ility

$%e c%ance of introducing a defect into yourprogram is directly proportional to t%e si1e oft%e c%anges you ma&e

Perfection is impossi*le .rite as little code as possi*le

Don(t fix w%at isn(t *ro&en

2xplains re-use


17/27

0aw Of Simplicity

$%e ease of maintenance of any piece ofsoftware is directly proportional to t%e simplicityof t%e indi,idual pieces

6ot of t%e w%ole system+ just t%e indi,idual pieces Stated differently+ is in,erse to t%e complexity"

Simplicity is relati,e+ largely to ,iewpoint

8ow simple do you %a,e to *e/ Perspecti,e of anot%er programmer w%o(s ne,er

seen your code

#e consistent


18/27

.%at Is a #ug/

Programmer(s Intentions

=ncertainties can *e resol,ed *y:

Comments

Spec 35easona*le programmer4

ssume %es%e meant to do w%at is *est for t%e user

=ser 2xpectations

Specs t%at ,iolate user expectations are spec *ugs

If t%ere(s a conflict+ it(s 3majority rules4

>ou can also add a preference+ *ut t%at adds complexity


19/27

.%ere Do #ugs Come 9rom/

Complexity

$%e *ox wit% a million unla*eled *uttons

Misunderstandings

Particularly of language words+ sym*ols+ functions+etc"


20/27

30aw4 of $esting

>ou don(t &now it wor&s unless you(,e tried it"


21/27

pplication in 9OSS

Must be more hardcore0argely pro*lems wit% geograp%ic distri*ution

8ere(s w%ere I tell you some t%ings to do+ *ut yous%ould still ma&e up your own mind"


22/27

Difficulties of Design in 9OSS

Speed of c%ange can *e limited

5e,iews

C%ec&in Procedures

0ac& of Some*ody to $al& $o I5C %elps;

$ime a,aila*le can *e limited

Designer(s $ime

8a,e to communicate designs 'uic&ly Implementer(s $ime

8a,e to *e a*le to read design 'uic&ly


23/27

Communication *andwidt% is limited

8a,e to type to communicate design

6o w%ite*oard+ etc"


24/27

De,elopers pic& w%at to wor& on

May not want to conform to design

May not want to wor& on refactoring


25/27

Solutions

2xtreme consistency

If you can(t communicate a design+ it %elps if t%eexisting code already wor&s t%e rig%t way

#rief communications Code re,iews

2xtensi,e de,eloper documentation

0ots of attention to new*ies #e nice


26/27

5ead support mail

5ead *logs a*out your product

#ut don(t e,er let your detractors write yourre'uirements"

Sur,ey your users

8a,e some*ody w%o lo,es refactoring


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$%e 2nd: ) @

%ttp:www"codesimplicity"com

max!codesimplicity"com
http://www.codesimplicity.com/http://www.codesimplicity.com/

Documents

Code Simplicity Open Source Design